Typical of electric ignitor probe assemblies are the sparking or discharge type, which require high voltage and fire by charging a capacitor, and the glow plug type which employ high amperage to generate heat. As is known in the art, oil can bring the initial temperature of the boiler into operating ranges relatively quickly after which the boiler can be switched over to a different fuel such as coal.
Irrespective of the fuel, the ignitor must be able to withstand very high temperatures encountered initially by high energy employed for ignition and subsequently, by virtue of being positioned in the midst of the burner flame at least until the boiler operation temperature is reached and in some environments, indefinitely. Boilers of the type contemplated herein are very large dimensionally and hence, the ignitor probe assembly can be positioned ten feet or more into the burner.
As might be expected, the ignitor probe assembly will eventually succumb to the high temperature environment not so much by melting of any components but rather due to the break down of the insulation and subsequent short circuiting. Removal of the ten foot assembly can be a time-consuming task particularly where space for withdrawal is limited. Nor, is disassembly an easy task as the prolonged heat environment tends to bond the engaging components together almost permanently as well as aging and making brittle the electrical wire and its insulation used to carry power to the probe tip.
Assemblies of the type known heretofore for ignition of these burners have employed an insulator comprising cloth, tape, mica and like materials in combination. A primary failure that has been encountered is of the insulator resulting in a short necessitating removal of the assembly, and then the ignitor tip for replacement of the insulator. In time, the wire can be cut back sufficiently or otherwise damaged to the extent that it must also be replaced. Despite the long standing existence of this problem, no ignitor assembly presently known has been able to withstand long periods of use without the failure discussed herein.